This invention relates to surfboards, and more particularly to a variable angle fin and mounting box assembly for such boards which enables the rider to "tune" the the performance of the surfboard by adjusting the angular relation of a conventional fin with respect to the longitudinal axis of the board thereby changing its maneuvering characteristacs to adapt to the various existing surfing conditions. As used hereinafter the term "surfboard" includes surfboards, long and short boards, boogie boards, sailboards, and other similarly-hulled watercraft which are maneuvered by the riders shifting their weight on the hull.
The need for an adjustably-mounted fin on a surfboard has been recognized by the art for providing surfboard stability and variable maneuvering characteristics depending on wave conditions and the weight of the rider. Such conditions were recognized in U.S. Pat. No. 3,308,493 issued on Mar. 14, 1967 to Frederick A. Lambach. In this patent the single fin was made adjustable in a direction parallel to the longitudinal axis of the surfboard, primarily to accomodate riders of different weights and their locations on the boards. A similar construction is shown in U.S. Pat. No. 3,564,632 issued on Feb. 23, 1971 to a W. L. Bahne Jr.
It should be noted that in each of the above cited patents, the length of the finbox is much longer than the length of the fin base to permit its longitudinal movement. Furthermore these patented devices required the use of a specially designed fin.
U.S. Pat. No. 4,493,665 issued on Jan. 15, 1985 to Edward M. Liddle recognized the need to adjust the angle of the fin with respect to the longitudinal axis of the surfboard to suit the weight of the rider, level of skill, and surfing conditions. These objects were met by providing a pair of elongated curved fin boxes, one on each side of the surfboard, of a length much greater than the fin base for longitudinally adjusting the position of the fin on the board as well as varying the angle of attack, both simultaneously, which may adversely effect the design characteristics of the surfboard and complicate its "tuning" by the rider.
In U.S. Pat. No. 4,733,496 issued on Mar. 29, 1988 to Peter Wallner, a single rudder-type fin was designed to enhance maneuverability of the surfboard through a two-piece construction, namely a fixed forward section and an aft pivotal section rotabably therein with respect to the longitudinal axis of the surfboard.
In the above cited patented art, the fin box was necessarily constructed to be much longer than the fin base to allow adjustment, and the fin was of a special design to achieve the desired results. A larger fin box than the fin base provides a greater water drag coefficient.